Spinneret surface finishing



United States Patent Ofiiice 3,349,522 Patented Oct. 31, 1967 3,349,522SPINNERET SURFACE FINlSHlNG James Stanley Cobb, Jr., Martinsville, Va.,assignor to E. I. du Pont de Nemours and Company, Wilmington, DeL, acorporation of Delaware No Drawing. Filed July 27, 1965, Ser. No.475,238 3 Claims. (Cl. 51--324) ABSTRACT OF THE DISCLOSURE After normalfabrication steps which leave protuberances, the face of a spinneret isfinished by abrading it to remove the protuberances, polishing theabraded face on a long nap cloth to remove burrs, lapping the face andthen polishing it on a no nap cloth.

This invention relates generally to the extrusion of viscous organicmaterials and more particularly to procedures involved in thefabrication of spinnerets adapted for use in the spinning of syntheticfilaments.

Experience has shown that a sharp edge is needed at the exit of eachspinneret capillary to insure a better and more uniform product. Sharpedges also improve wiping efficiency. Wiping is the removal during aspinning interruption of the organic stalactites which form at thecapillary exits during the spinning process. It further has been foundthat a bright finish on the spinneret face is desirable for preventionof corrosion at these sharp edges.

Normally, the method used to form capillaries in a spinneret blank is toeither drill or punch or use a combination of these steps, leavingprotuberances or burrs on the face of the spinneret. These protuberancesare removed by abrading the spinneret face, e.g., by lapping, grinding,or rubbing on abrasive paper. All of these steps put a burr on theinside edge of each capillary. When such burrs are removed with a sizingpunch or broach, another lapping, grinding, or rubbing step is requiredto remove the metal forced out to the face of the spinneret by thebroaching step. Instead of removing burrs with a sizing punch or breach,burr formation within the capillary is sometimes avoided by pluggingeach capillary with glass or metal inserts before removal of theprotuberances. The inserts are not removed until completion of thesurfacefinishing steps. Both of these techniques are time consuming andcostly.

The major objective of this invention is to provide an improvedfinishing technique for removal of burrs from capillary walls whileproviding a bright finish on the face of a spinneret and sharp edges atthe capillary exits. Another objective is to provide a less-costlytechnique for finishing spinnerets. More specifically, the object ofthis invention is to avoid the use of sizing punches, broaches rcapillary plugs in the fabrication of capillaries which are not onlyfree from internal burrs but also have sharp exits.

With these and other objects in view, the presently disclosed methodcomprises generally the steps of machining capillaries which exit at theface of a spinneret blank, removing protuberances left on the face ofthe blank during the machining step by abrading, removing the burrsformed inside the capillaries during the protuberance removal step bypolishing on a long nap cloth, resharpening the exits of the capillariesby lapping, and putting a bright finish on the spinneret face bypolishing on a no nap cloth.

Any of the known techniques can be used to form a spinneret plate orblank and to form the lead-in holes and capillaries, e.g., the spinneretpunching machine described by Thomann et al. in U.S. 2,709,492. Afterall of the capillaries are punched, there are a number of protuberancesremaining on the face of the spinneret. Depending upon the techniqueused, either the capillary is partially opened in this protuberance or,using the technique described by Thomann et al., the capillary does notbreak through the protuberance.

After the punching is completed for all the capillaries, the finishingtechnique of this invention calls for removal of the protuberances by anabrading step, e.g., by lapping, grinding, or rubbing (by hand ormechanically) on a fine abrasive sheet. The abrasive sheet is mounted ona flat plate so that, in addition to removing the protuberances, theface of the spinneret is made flat. However, this step leaves ascratched sufaoe and, in addition, removal of the protuberance usuallyleaves a burr inside the capillary. The next step is to place thespinneret face down on a metal wheel covered by a long nap felt cloth.The polishing wheel is then rotated and the spinneret reciprocated onthe wheel so that a uniform multi-directional cut is achieved. It isalso sometimes desirable to rotate the spinneret as well as thepolishing wheel. While the mechanism is not completely understood, it isbelieved that the fibers or filaments of the long nap reach up into thecapillary and pull or abrade away the burrs inside the capillary. Thisstep is continued until the burrs are removed. However, in doing this,the edge or exit of the capillary to the face of the spinneret becomesrounded. It is now necessary to lap the face of the spinneret to be surethat it is fiat and to sharpen the capillary exits. However, this doesnot put on the high or bright finish that is necessary to achieve goodcorrosion resistance. Consequently, a final polishing step is carriedout with a rotating no nap cloth.

A typical example is the fabrication of a spinneret for spinning nylonfilaments from type 430 stainless steel, which spinneret has roundcapillaries 0.009 inch in diameter and 0.012 inch long. Drilling alead-in hole in the spinneret blank is the first step in the preparationof each capillary. In a series of drilling and punching steps, the finalcapillary is formed but does not break through a protuberance left onthe spinneret face. This protuberance or nub is removed manually byrubbing the spinneret on 400 grit and then on 600 grit wet paper(mounted on a fiat plate) until all the nub is gone. This step, however,leaves a rough capillary exit, that is, there are scratches on the faceof the spinneret which run through the capillary and burrs are bent intothe capillary. The burrs are removed by polishing on a rotating metalwheel, i.e., a metal wheel which is covered with a long nap, pluckedpile cloth of uniform, sheared, virgin wool (Knoxall No. 1,118 nappedcloth, manufactured by EH. Beste Company, Boston, Mass). After the clothhas been charged with chrome rouge and a light machine oil, this step iscontinued until the burr is removed, normally approximately fiveminutes. Burr removal leaves the 'hole edge rounded to an 0.000080" to0000150" radius. This radius is measured by an interference microscope.The next step is a micro-lapping operation in which the spinneret isplaced in a lapping machine (the Lapmaster made by John Crane Company)which has a wheel on which the spinneret plate is placed and constrainedby a ring-shaped holder. With a weight on the plate, it walks around theinside periphery of the holder as the wheel is rotated. In the preferredmethod, this is accomplished by using a 0.5 to 1.0 p.s.i. lappingpressure with a five micron (grit size) compound in a mixture of lightoils similar to kerosene (No. 3 Lapping Vehicle, John Crane Company) andthe lapping continued for approximately seven minutes. The time requiredto lap the hole de'ge sharp is a function of the lapping pressure andthe number of interference rings. In general, the lapping pressure isadjusted so that the lapping time is approximately thirty seconds perinterference ring. An alternative to this is to use a coarser compound,e.g., 1,700 grit compound, for approximately one minute. Care must betaken to insure that this micro-lapping is not done too long, otherwisethis step will put a burr back into the capillary. The final polishingstep is accomplished by using a no nap cloth on the polishing wheel. Anylon satin, charged with chrome rouge and a light machine oil, is usedin this example. The result is a burr-free edge with a radius between0.000010" and 0.000050".

Depending upon the materials of construction, it is of course obviousthat various times and abrasives could be used. It should also beapparent that the techniques disclosed herein can be used forcapillaries with odd-shaped cross sections. Other adaptations andmodifications inherent in the practice of this invention will occurreadily to those skilled in the art and, accordingly, its extent isintended to be limited only by the scope of the appended claims.

Having thus described the invention, what is claimed as new and desiredto be secured by Letters Patent is:

1. In a spinneret fabrication method including the preliminary step ofmachining a capillary hole in a spinneret blank thereby leaving aprotuberance on one face of the spinneret blank, a finishing techniquecomprising the steps of: abrading said face to remove the protuberance;polishing the abraded face on a long nap cloth to remove burrs fromwithin said hole; lapping said face just sufiiciently to sharpen thehole exit; and polishing the face on a no nap cloth.

2. In a spinneret fabrication method including the preliminary step ofmachining at least one capillary hole in a metal spinneret blank therebyleaving a protuberance on one face of the spinneret blank, a finishingtechnique comprising the steps of: rubbing said face on an abrasivesheet to remove said protuberance; polishing the abraded face on arotating wheel covered with a long nap felt cloth; lapping the polishedface just sufiiciently to sharpen the hole exit; and polishing said faceon a no nap cloth.

3. In a spinneret fabrication method including the preliminary steps ofmachining a plurality of capillary holes in a spinneret plate therebyleaving protuberances on one face of the spinneret plate, a finishingtechnique comprising the steps of: rubbing said face on a fiat platecovered with an abrasive sheet; polishing said face on a rotating metalwheel covered with a long nap cloth previously charged with chrome rougeand a light machine oil, thereby removing burrs from within thecapillary holes but leaving rounded edges at the capillary hole exits;lapping the polished face just sufficiently to sharpen said edges; andpolishing said face on a rotating wheel covered with a no nap cloth.

References Cited UNITED STATES PATENTS 1,952,025 3/)1934 White l882,115,402 4/1938 Spaanbroek 51323 X 2,658,414 11/1953 Issartial 51-323 X2,709,492 5/1955 Thomann et al 72l 2,923,969 2/1960 Thorpe 188 LESTER M.SWINGLE, Primary Examiner.

1. IN A SPINNERET FABRICATION METHOD INCLUDING THE PRELIMINARY STEP OFMACHINING A CAPILLARY HOLE IN A SPINNERET BLANK THEREBY LEAVING APROTUBERANCE ON ONE FACE OF THE SPINNERET BLANK, A FINISHING TECHNIQUECOMPRISING THE STEPS OF: ABRADING SAID FACE TO REMOVE THE PROTUBERANCE;POLISHING THE ABRADED FACE ON A LONG NAP CLOTH TO REMOVE BURRS FROMWITHIN SAID HOLE; LAPPING SAID FACE JUST SUFFICIENTLY TO SHARPEN THEHOLE EXIT; AND POLISHING THE FACE ON A NO NAP CLOTH.